Features: This voltmeter's wiring is simple, it only need to connect two wires, the red wire is to connected to positive pole, the black wire is to connected to negative pole, There is protection when the wires aren't correctly connected, the electric circuit won't be bumed This voltmeter doesn't need external drive working power, it can work with measuring voltage, the working voltage's range is 4.5-30V Toreach the best measurement accuracy, this voltmeter will automatically move the decimal point's position according to the different measuring voltage, When it measures the voltage below 10V, it will display two places after decimal point, when it measures the voltage above 10V, it will display one place after decimal point This voltmeter can be used to measure the storage battery's voltage in motorcycles and cars and also can grasp the storage battery's status, It also can be used to measure other voltage Note: 30V is the voltmeter's maximum operating limited voltage, please leave enough margin when working, to avoid voltmeter's permanent damage because of electrical spark, power supply ripple, or other too high abrupt change of voltage This voltmeter didn't do moisture-proof, waterproof, shockproof, anti-oil processing, please be careful or handle by yourself when using Specifications: Measuring range: 4.5V-30V DC Minimum Input: DC 4.5V Maximum Input: DC 30V Accuracy: 1%(+/- 1word) Display Type: 3 0.36" LED tube Display Color: Red/Blue/Green Refresh speed: About 200ms/time Current consumption: less than 20mA, usually 5-15mA Working temperature: -10~65 Dimensions: 34x23x17mm/1.34x0.91x0.67" (LxWxT) Opening Size: 30x20mm/1.18x0.79" Quantity: 1 Pc Note: Please allow 1-3mm error due to manual measurement. pls make sure you do not mind before you bid Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you Package Includes: 1 x Digital LED Display Voltmeter